It might depend a lot on your structure but usually you create a specific account for sales/cogs (call it intercompany) and a fiscal position called intercompany which will replace the standard account with intercompany account. You assign this fp to any partner related to softer company.

Doing so, all your intercompany transactions will be recorded/isolated into specific accounts.

When doing mono company report you obviously select both normal and intercompany accounts.

When doing intercompany/consolidation reports, you rule out the intercompany accounts.

Same might apply on your analytical accounting (set a default to intercompany specific account for the partners being sister company)

My implementation of odoo includes 45 different operating companies under a single umbrella.

Are there ways to eliminate inter-company transaction so that when I run reports across multiple companies j don't have to clutter the reports with a bunch of lines.

For example:If parent company A sells $500 worth of product to child company B, on a Consolidated financial report that line would not be displayed , (assuming the balance is 0, as it always should be)

My reasoning is that we do a ton of sales between different inner companies.

I have a feeling that this solution will include consolidated accounts, but I'm.not sure.